CAIE A-Level Physics A2 24.1.5 Ir I0 Z1…fficient

(a)

Table 8.1 shows some data relating to the properties of air, gel and body tissue. The data are given to three significant figures.

Table 8.1

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(i)

Complete Table 8.1 by calculating the missing values to three significant figures. Use the space below for any working that you need.

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(b)

Use the information in (a) to calculate the intensity reflection coefficient for:

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(i)

an air-tissue boundary

intensity reflection coefficient =

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intensity reflection coefficient $=\left(Z_{1}-Z_{2}\right)^{2} /\left(Z_{1}+Z_{2}\right)^{2}$ $=(1680000-440)^{2} /(1680000+440)^{2}$
= 0.999

(ii)

a gel-tissue boundary.
intensity reflection coefficient =

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intensity reflection coefficient $=\left(Z_{1}-Z_{2}\right)^{2} /\left(Z_{1}+Z_{2}\right)^{2}$ $\begin{aligned} =(1680000-1680000)^{2} /(1680000+1680000)^{2} =0 \end{aligned}$

A1

(c)

Use your answers in (b) to explain why gel is applied to the skin during ultrasound scanning.

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CAIE A-Level Physics A2 24.1.5 Ir I0 Z1 Z2 2 Z1 Z2 2 For the Intensity Reflection Coefficient Topic Practice

Question 1

Question (a)

Question (i)

Question (b)

Question (i)

Question (ii)

Question (c)